Condition control means



April 4, 1944. c. G. KRONMILLER CONDITION CONTROL MEANS Filed April 15,1942 INVENTOR Carl (-1 Kromuillar ATTORNEY Patented Apr. .4, 1944CONDITIONOONTROL MEANS Carl G. Kronmlller, Minneapolis, Minn usignortoMinn eapolls-Honeywe Minneapolis, Minn, a c Application April 15,1942, Seriai No. 4%,063 1'? Qlaims. (CB. 236 263 This invention relatesto means tor controlling physical condition such as temperatme,humidity, or pressure, but more particularly to a control means forproviding close regulation of a condition in a condition control systemof the type wherein an inherent time lag exists between the time acondition changer is set in operation to establish a particularcondition value and the time when the operation becomes. eflective toestablish such value.

It is a well known characteristic of all heating systems, for example,that a. definite time elapses between the time increase thetemperaturevalue or a space and the time the temperature or the space begins torise as a result of the additional heat supplied thereto. Consequently.y the tim the temperature of the space has risen to the desired value,and operation of the heating minated,

to the space to raise above the desired value.

Such an objectional condition, well known in the art as overshooting," iparticularly present in heating systems of the type wherein the heatingapparatus is started and stopped in accordance withspace temperaturessuch as stokers. oil burners, and the like, the overshooting resultingfrom extended operation thereof over long periods of time. In the caseor stoker operation wherein the fuel is fed at a rate in excess-01' thecombustion rate thereof, a. mass of unburned fuel accumulates in thecombustion chamber dur-- ing such an extended period of stoker operationwhich continues to heat the heat transfer medium long after operation ofthe'stoker has been discontinued. The reserve heat thus produced theheat transfer medium if which the medium has heat in the case of a hotwater system.

Overshooting might as readily result,

the system is one in however, in

is stored as a result of prolonged heat increasing activity of theheating means, as might be caused, for example, by a low rate of heattransoperates to satisfy a condition indicative of a need for prolongedoperation thereof.

any heating system wherein a. reserve of heat a heating means operatesto means has been teris further augmented by reserve heat stored instoring capacity. as

ll Regulator Company, orporation of Beiaware Another object is tprovide, in a condition cont'roi system of the type descrihed whereincondition changer is controlied icy means reopen sive to variations inth value of the condition, means operable independently of the controlmeans and variations in the value of the conch tion for preventingcontinuous operation of the condition changer when the same operates tosatisfy a condition indicative of a need for prolonged operationthereof.

A further object is to provide means for preventing continuous operationof the condition changer when the control means is shifted from oneposition to the other and the condition changer operates to change thecondition from a value of one range to a value of the other.

The invention has a particularly advantageous application to temperaturecontrol systems of the day-night type in which a space is maintained atone temperature value during the night, and timed means is provided forshifting the system from night to day operation. In such a systemprolonged operation of the heating means extending over a period oftime, commonly referred to as a morning pick-up period, is required toraise the temperature of the space from the low night value to thenormal daytime value.

Accordingly, an object of this invention is to provide, in a day-nightsystem of the type described, a means operable by the timed means forcausing intermittent operation of the heating means when the sameoperates to raise the temperature or the space from the night to the daytime value.

Another object is the provision, in a day-night system of the classdescribed, oi. means operable by the tfined means for into ttentiyactuating the control means in a manner to provide intermittentoperation oi? the heating means in a sequence of predetermined intervalsextending over a predetermined period of time following the return ofthe control means to the day time setting thereof.

Q Another object is to provide, in a day-nigl1t system in which atimedmeans is set in operation by the manual adjustment of the night setmeans. a one-way mechanism operable to intermittently actuate thecontrol means by the timed means. but inoperable upon operation of themanual means.

Other objects notspeclncally recited hereinabove will become manifestwith a reading of the tollowing specification reference being had to theaccompanying drawing in which Figure 1 is a schematic view of atemperature control system wherein the temperature control means of thisinvention is utilized,

Figure 2 is a side elevation of the temperature control means as shownmounted on a vertical wall or the like,

Figure 3 is a front elevation of the temperature control means as shownmounted in Figure 2, w

Figure 4 is adetailed view of and the follower, and

Figure 5 is a fragmentary view of the contact carrying member and theinterrupter arm, and

Figure 6 is a fragmentary view of the casing the cam means for thetemperature control instrument.

Referring to Figure 1, the numeral i generally designates a furnace of awell known warm air type having a bonnet (not shown) and an air.

duct ll leading therefrom which communicates with a space i2 which isheated by air warmed in the bonnet and transferred to the space 12through the duct 1 I.

Fuel is fed to the furnace l0v by stoker l3, the operation of which iscontrolled by a thermostat generally designated by the numeral l4,situated in space 12. The thermostat 14 comprises a'bimetallic clement Imovable in response to variations in'the temperature value of space l2and a contact carrying member l6 secured thereto for movement therewith.The member 18 carries a pair of movable contacts l1 and i8 sequentiallyengageable with fixed contacts l9 and 20 respectively.

Thermostat 14 controls the energization of a relay generally designated2| which is supplied by a transformer generally indicated by the numeral22. Transformer 22 comprises a secondary winding 23 and a primarywinding 23 connected to a suitable A. C. source (not shown).

The relay 2i comprises a relay coil 25, an armatnre 26 actuable thereby,and a pair of switches 21 and 23 in turn actuated by the armature 26.Energization of relay coil 25 causes movement of armature 26 to theleft, and movement of switch blades 29 and 30, operatively connectedwith armature 25, into engagement with fixed contacts 3| and 32 ofswitches 21 and 28 respectively. When the coil 25 is deenergized, theswitches return to their open positions as shown, by means of anysuitable biasing means (not shown). From the foregoing it should now beapparent that the thermostat I4 and the relay 2| are of the well knownholding type and that the switch 21 is for the purpose of maintainingthe energization of coil 25 and thereby holding the switch 28 in aclosed condition for a definite period of time as determined by thedifferential of the thermostat M. The switch 28 controls theenergization of the stoker l3 which is supplied by a suitable source ofpower through supply lines 33 and 34, the switch 28 being insertedbetween the supply line 33 and the stoker l3.

In the operation of Figural, with the parts in their positions as shown,the temperature of the space I2 is at or above a normal-value in whichcase the thermostat l4 issatisfied. When the temperature in thespace 12drops, the member l5 sequentially engages the contacts 19 and 20respectively, which completes a, circuit for energizing the coil 25 asfollows: From secondary winding 23 through aco'n'ductor 35, contact l9,

member l6,.contact 28, a conductor 36, coil 25 and a conductor v31 backto secondary winding 23. The switch 21 is then closed which completes asecond circuit for energizing coil 25 as follows: from secondary winding23 through conductor 35, contact l9, member l6, bimetallic element iii,-a conductor 38, blade 29, contact 3!. a conductor 39, coil 25, and aconductor 31 back to secondary winding 23. The switch 28 closessimultaneously with the closing of switch 21 and completes a circuit tothe stoker 13 as follows: from the source of power through the supplyline 33, fixed contact 32, switch blade 30, a conductor 48, stoker l3,and supply line 34 back to the source of power. erates to feed fuel tothe furnace III, the combustion of the fuel creating heat whicheventually is dissipated in the space l2. When the temperature in thespace i2 rises to a predetermined point, the-member 15 moves out ofengagement with the fixed contact 28 whereupon the first circuit forenergizing the coil 25, as traced herein- 21, 28 are closed, and thestoker l3 continues to operate to supply heat to the space I2 until thetemperature therein rises to the normal value whereupon the member l8moves out of engagement with the fixed contact IS. The holding circuitenergizing the coil 25 is then opened, and the switches 21, 28 return totheir open positions, thus terminating operation of the stoker l3.However, because of the time delay in transferring the heat from thefurnace In to the space '12, which is an inherent characteristic Of allheating apparatus, and particularly because of the fact that the stokerl3 feeds fuel to the furnace ill at a rate in excess of the combustionrate thereof, a mass of unburned fuel has accumulated after theoperation of the stoker l3 has been terminated. The residual heatthereafter created by the continued burning of the accumulated mass offuel in the furnace continues to raise the temperature of the space l2above the normal value thereof thereby creating the objectionalcondition commonly referred to as overshooting. Such a condition isparticularly present when the demand on the furnace necessitatesprolonged operation thereof over an extended period, as in the case of amorning pick-up period for example. The purpose of this invention is toprovide meansv associated with the thermostat M for providingintermittent operation of the stoker l 3 when the thermostat l4 respondsto a condition in space [2 indicative of a need for a prolongedoperation of the stoker I3. The residual heat stored in furnace ID as aresult of the operation of the stoker 18 during such intermittentperiods being thus utilized in raising the temperature of the'space l2to its normal value and preventing an overshooting thereof.

While in Figure 1 I have illustrated a particular condition controlsystem, I wish it to be understood that the control means of thisinvention is applicable to any condition control systhe control meansmay be applicable to a heating system in which a hot water orsteam-furnaceemploying an oil or gas burner as well as a stoker is used.The control means may also be applicable to control a motor operator incontrol of the usual check and draft dampers of a furnace or of a valvein a heating supply line.

Referring now to Figures 2 and 3, it will be seen that the thermostat IIis of the day-night type, the bimetallic element i5 being movablebetween day and night settings. The'thermo- The stoker l3 then opstat I4is generally similar to the thermostat described and claimed in myco-pendlng application Serial No. 137,725, filed April 19, 1937,entitled Thermostat, which has matured into Patent No. 2,280,651,granted April 21, 1942. Accordingly, the instrument will be describedbut briefly herein, reference with respect to details of constructionbeing had to the aforesaid copending application. The thermostat 14comprises a base 4! and an insulation plate 42 supported thereon andriveted thereto. A bracket 43 suitably secured to the plate 42 pivotallysupports the bimetallic element at 44 for swinging movement parallelwith the base H. The element 15 is U-shaped having the contact carryingmember i5 riveted thereto at one end thereof as best seen in Figure 5.The member I6 is bifurcated, the outer iurcation (see Figure 3) beingbent back at the base and doubled back at the tip to accommodate aresilient finger 45 which carries the movable contact 51. The fixedcontacts 19 and are adjustably carried by rigid supports and 47respectively, which are suitably secured to the insulation plate 42. Theother end of element i5 is operatively linked to a lever 48 by means ofan insulation piece 45, the lever 48 being pivotally supported on thebase 4| at 5ll for swinging movement parallel to the base 4!. The otherend of lever 48 carries a screw 5| which engages a cam 52 supported onbase 4| for rotation about the axis 55. An indicla bearing dial isconnected to cam 52 for rotation therewith about the axis 53 and cooperates with a pointer 54 integrally termed with the base 4! toindicate a position of element l5 providing a particular temperaturecontrolled point of the space I1 It will be understood that movement ofthe dial 55 provides an adjustment oi the element i5 over a range ofvalues provlding daytime temperature control of the space- 52.

A casing 56 suitably secured to the base ll contains a cloci: preferablyis of the type disclosed in Andrew G. McNicoli Patent No. 2,108,776,issued February 15, 1938, entitled "Starting mechanism. The clockmechanism comprises a winding stem 5? which may be manually rotated bymeans of a handle 53 operatively secured to the stem 5? to set themechanism in operation for a predatormined time period, which for thepurposes of this invention may be in the neighborhood at 11 or 12 hours.The mechanism further cornprises a slip friction mechanism which permitsreverse manual movement of the stem 51 for purposes of resetting theclock mechanism in the case of an over-winding ofthe stem 5?.

A lever 59 freely mounted on the stem 51 is provided with an upturnedear Gil-which extends upwardly through a slot 6| formed in a disc 52which is concentric with the stem 51. The disc 52 is provided with a hub85 which is secured for rotation with the stem 51 by means of a screw54. A spring 65 is wound about connected at one end to the ear 6!! andat the other end to the screw 64. The spring 85 is wound about the hub53 in such a manner as to bias the lever 59 in a counter-clockwisedirection. With the partsin their positions as shown in Figure 3, theclock mechanism is inoperative and the distal end 55 of lever ment 5! onlever 48 to resiliently urge the screw 5| into engagement with the cam52. It will be noted that the car 50 is some distance from the leadingedge 58 oi the slot 5! which permits mechanism (not shown) which 59engages an abut-.

the hub 53 and 'tance between the nails moving a knob 85 movement 01'the lever 45 by action of the cam 52 on the screw 5! in adjusting theoperating point of the instrument over the daytime range. It will befurther'notedthat the car 60 is at a considerable distance from thetrailing edge 55 of the slot 61. Accordingly, the disc 52 movesrelatively with respect to the lever 59 when the stem 57 of the clockmechanism is moved clockwise to set the clock mechanism in operation.When the disc 62 has moved through thediscar 69 and the trailing edge 59of the slot H, the disc 52 picks up the lever 59 which then moves out ofengagement with the abutment 51. The element l5 then pivots about thepivot 44 in a counter-clockwise direction by action of a compressionspring 70 which is suitably mounted between the bracket 43 and theelement 15. Accordingly, because of the connecting link 49 betweenelement l5 and lever 48, lever 45 also pivots counter-clockwise aboutits pivot 55 until a screw 'li carried by a lever 12, also pivotallysupported at 55, engages a cam 13. Cam 13 is also mounted for rotationabout the axis'53 of cam 52 and is operatively con' nected to an indiciabearing dial (4 which also cooperates with the pointer 54 to indicate aposition of element 55 providing a particular control point of a rangeof values covering night time operation of the instrument. The lever 72is biased towards the lever 48 by means of a spring 15, movement in thatdirection being limited by engagement of abutments l8 and 11 provided onthe levers 45 and 72 respectively. It should be understood that spring75 is stronger than spring we and that lever 72 acts as an integral partof lever 48 in adjusting the element it when in itsnight time position.Accordingly, the spring it does not yield by action of the spring 70 inurging the element is in a counter-clockwise direction. However, thespring 75 does yielt when an attempt ,is made to adjust the instrumentto a higher night time value than the existing daytime value asdescribed in my copendlng application referred to hereinabove.

An indlcia bearing dial i8 i frictionally connected to the winding stem5? by means oi a flexible blade iii. The connection between the dial l8and the stem. 57 is such that the dial normally rotates with the stem5i, but may be moved relatively wlth'respect thereto laymanoperativelyconnected with-the dial it. The indicia on the dial it appears through awindow 5i formed in the thermostat casing 82 and cooperates-with apointer 53 formed integrally with the casing 52 to indicate the durationor" operation of the clock mechanism as will hereinafter appear.

Rlgidly-secured to the base 4i is a post 58 provided with apivot pin 55upon which is pivoted a lever 55. Lever 58 is confined to limited axialmovemntwlth respect to the pin 55 by means oi a lock washer 57. Thelever 55 is spaced with respect to the casing 56 by means or a sleeve 85through which extends ascrew 59 which is received in the casing 56, asbest seen in Figure 5. The screw 59 extends through an arcuate slotconcentrically formed" in lever 55 with respect to the pivot pin 55.Thus, the I lever 55 is free to swing about the pivot pin 55sufllclently to actuate the contact carrying member ii. For this purposethe free end, oi lever 56 is struck up at right angles adjacent shown inFigure 4.

I the space 12 of 50 F., as shown by ting the thermostat as previouslyexplained. The-thermostat M then 4- means of a piece of tubularinsulation 9! which is slipped over the turned up end of lever 86.

As will be seen in Figure 4. the disc 62 carries a cam 92 which isprovided with a series of equally spaced radial projections 93. The pro-1 jections 93 are arranged concentrically with respect to stem 51 andare engageable with a follower pin 94, secured to a struck-up portion 95of the lever. 86. Under certain conditions to be pointed outhereinafter, the projections 98 provide intermittent movement of thelever 96 and therefore the member it to intermittently disengage thecontacts i1, respective fixed contacts i9 and 28. It will be understoodthat the arrangement of lever 89, cam 92, insulation piece 9!, andmember i8 is such that the contacts i'l, l9 and i8, 20 are engageablewhen the parts are in the-position shown in Figure -3 and that thecontacts are disengaged when the follower pin 9% occupies the positionwith respect to a projection 93 as The cam 92 is secured to the disc 62by means of rivets 96 which extend through slots 98 provided in the cam92. The slots 98 provide a lost cam 92. It will be noted that the lowerportions of the slots 98 are at a greater radial distance from thecenter of rotation of the disc 62 than the upper portions of the slots.Accordingly, with the parts in the position as shown in Figure 3,movement of the disc 62 in a clockwise direction to set the clockmechanism in operation causes inward movement of the cam 92 with respectto the disc 62, sincethe' pin 96 resiliently bears against one of theprojections 93. This causes the cam 92 to-mov inwardly sufficiently toclear the pin 96. The provision of the inward movement of the cam 94 isfor the purpose of providinga one-way mechanism for actuating lever atand thereby preventing rapid recycling of the heating system should thecontacts be closed at the time the clock mechanism is set in operation.It will be further noted that the upper portions of the slots 98 areformed, arcuately with respect to the disc 62. This is for the purposeof preventing inward movement of the cam 92 when the disc drives thesame in a counter-clockwise direction and the pin. 94 exerts a radialthrust against the rivets 99, as shown in Figure 4.

Withthe parts of the thermostat in the position shown in Figure 3, theclock mechanism is inoperative, the element I is in its daytime po--sition and the space ture of 70 I2 is at or above a tempera- F. If it isnow desired to shift the N from their ly the need for raising operateson a night time setting until the first projection 93 of the cam 92engages the pin 95. At this time the lever 59 reengages the abutment 81and shifts the element iii to its daytime setting. Since the temperaturein thespace is undoubtedly low at this time, the contact ll, 19 and i8,20 are engaged andthe stoker i8 is set in operation, after which thefurnace operates to supply additional heat to space I2. In spite of thefact that the thermostat I4 is now, set to respond to a conditionexisting in space i2, name- .the temperature or the spacei? from 50 to70 F., which'condition is indicative of a need for prolonged operationof the stcker It, the clock mechanism acts independently of thetemperature in the space 92 and furnace it through the cam 92 andinterrupter lever 86' to intermittently open the thermostat contacts tothereby control operation of the stoker I3 ina series of "oli" and on.periods until the last projection 93 has passed the fol- 1ower pin 9% asshown in Figure3. By thus interrupting prolonged operation of the stokeri3,

' overshooting of the space H is very substantially motion connectionbetween the disc 62 and the prevented and the residual heat stored infurnace it during the intermittent operation of stoker i3 is utilized togreat advantage in raising the temperature of the space from therelatively iow night time value to the normal daytime value.

. In practice, an hour and minutes has been found to be a satisfactorymorning pick-up period. In other words, an hour and 45 minutes ofoperation of the clock mechanism remains from the time the firstprojection 93 of the cam 92 engages the follower pin 96, after which iour the cam 92 designed ofi" periods and three "on periods follow. Inpractice, with as shown, the off periods average'15 minutes and the onperiods average 14 minutes. It will be noted that as each projection 93climbs forward over the pindl, the cam 92 is urged forwardly of the disc62 due to the biasing action of element 115 in a contact engagingdirection. This accounts for the on. periods being nearly as long as theofi periods despite theiact that the periods during which pin 9% wouldotherwise be in the bottom of the dwells between the projections 93would be relatively small as compared with the periods during which itwould be riding on the projections 93 so as to separate the contacts. Itwill be further noted that with the thermostat i4 mounted on a elementiii to its night time position in which will be controlled at atemperature a dial I8, and it this change be made at ten o'clock in theevening, for example, theknob 89 is rotated until the numeral It on dial18 appears in the window 8|, the dial 78 moving fric'tionally relativelyto the winding stem 51. If it is further perature of the space 12 bebrought back to 70 F. at, say eight o'clock inthe morning for example,the handle 58 is wound clockwise, the dial I8 desired that the tem-.

moving with it, until the numeral8 on the dial I8 appears in the window8i. During this setting oi the clock mechanism the cam 92 is movedclockwise past the pin 94 without actuating the contacts, as describedhereinabove. Likewise,

lever 59 moves away'irom-abutment 61 permitto move to its night settingsuch position.

vertical wall as shown, the interrupter lever 86 and cam 92 have 'atendency to return tothe position as shown in Figure 3 by means ofgravity. If it is desired, however, any suitable biasing spring may beused to return the members to It should also be .noted that theinterrupter mechanism does not interfere with the free movement or theelement It in a counter-clockwise direction. Consequently, if thetemperature of the space M reaches its day time value at a time when thesecond projection 93, for example, has just passed the pin 94, continuedactuation of the lever 86 has no eirect whatever on the operation of thestoker l3. Thus, it will be understood that the interrupter mechanism isoperative to provide intermittent operation of the stoker l3 only whenthe thermostat i4 responds to a condition of space means actuabiethereby,

or temperature values tion from one value this invention, I do not wishto be strictly limited thereto, but contemplate all such changes,omissions, substitutions, additions, and alterations as will naturallyoccur to'those skilled in the art without departing from the scope orspirit of this invention as defined by the appended claims.

I claim as my invention:

1. In a heating system, space, an element movable tions in thetemperature means for heating a in response to varia of said space,switch circuit connections controlled by said switch means when closedto initiate operation oi said heating means and when opened to terminateoperation thereof, means for selectively rendering said element Operableto close said switch means in response to a first range of said space,visual means for indicating the selected value of said firs range, meanfor selectively rendering said element operable to close said switchmeans in response to a lower range oi temperature values of said space,visual means for indicating a selected value or" said lower range, meansfor rendering said, element responsive to said lower range of values fora predetermined period of time and responsive to said first range ofvalues at the expiration of said period of time, means operableindependently of said element and independently of variations in thetemperature or" said space for opening said switch means in a sequenceof predetermined intervals extending over a second predetermined periodof time following the expiration of said first period, and visual meansfor indicating the total duration oi said first and second periods.

2. In a'condition control system, a condition changer, means responsiveto variations in the value oi said condition for controlling operationof said condition. changer, and timing means as sociated with saidcontrol means for intermittently removing the same from control of saidcondition changer to prevent operation thereof during predeterminedintervals extending in a sequence over a predetermined period at timeduring which said condition changer operates to change said condia.substantially different; it would otherwise tend for much longer periodsLC value and during which operate continuously than those existingbetween said intervals.

3. In a heatingsystern, means for heating a space, means responsive tovariations in the tern perature oi said space for controlling operationof said heating means, said control means being movable between firstand second operating positions corresponding to first and secondtemperature ranges or said space to be maintained by said control meam,timed means for moving said control means between said first and secondpositions, and means operable by said timed means for controllingoperation or said heating means when the same operates to change thetemperature of said space iro'm said first to said second range.

4. In a heating system, means for heating a space, means responsive tovariations in the temperature or said space for controlling operation ofsaid heating means, said control means being movable between first andsecond operating positur'e ranges oi said space to be maintained by saidcontrol means, connections by which said control meansinitiatesoperation of said heating means when. the temperature oi said spacefalls below a value of said first or second range and terminatesoperation thereof when the temperature rises above said value 01' saidfirst or second meat being movable range, timed means for moving saidelement between said first and second positions, and means operable bysaid timed means for actuating said control means to intermittentlyinterrupt operation of said heating means when the same operates tochange the temperature of said space from said first to said secondrange.

5. In a heating system, means for heating a space, means rmponsive tovariations in the temperature of said space for controlling operation ofsaid heating means, said control means being movable between first andsecond operating positions corresponding to first and second temperatureranges of said space to be maintained by said control means, means forindependently adjusting said first and second operating positions,manual means for moving said control means from said first to saidsecond operating position, timed means for moving said control meansfrom said second to said first position, and means operable by saidtimed means for controlling operation of said heating means when thesame operates to change the temperature of said space from said secondto said first range.

6. In a condition control device, an element responsive to variations inthe value of a condition, switch means operable thereby, a timed means,means operable by said timed means for controlling said switch meansindependently of said element and of variations in the value oi saidcondition, said independent means being operable by said timed means tointermittently actuate said switch means in a sequence of predeterminedintervals extending over a predetermined period of time.

i. In a condition control device, an element responsive to variations inthe value of a condition, switch means operable thereby, said elementbeing movable between first and second operating positions wherein itoperates said switch means so as to maintain first and second conditionvalues, timed means for moving said element between said first andsecond positions, and means operable by said timed means torintermittently actuating said switch'nieans when said element moved toone of said positions.

3. in a heating system, means for heating a space, means responsive tovariations in the temperature oi said space for controlling operation ofsaid heating means, said control means being movable between first andsecond operating positions corresponding to first and second tempera"ture ranges or said space to be maintained by said control means, manualmeans for moving said control means irom said first to saidsecond'opersting position, timing means set in operation by said manualmeans, means for predetermining the period of operation of said elementin one of said positions, and means operable by said time means forintermittently actuating said control means at the expiration of saidperiod.

9. In a condition control device, an element responsive to variations inthe value of a condition, switch means operable thereby, said elebetweenfirst and second operating positions wherein it operates said switchmeans so as to maintain first and second condition values, a timedmeans, a manual means for moving said element from said first to saidsecond position and operable to set said timed means in operation,saldtimed means being operable to move said element from said second tosaid first position after a predetermined period of operation thereoi,and means operable thereafter by said timed means for intermittentlyactuating said switch means in a sequence of predetermined intervalsextending for the duration of operation of said timed means.

10. In a thermostat, temperature responsive means movable between dayand night settings for controlling temperature values thereof, timemeans associated therewith for moving said responsive means from saidnight to said day setting, and means operable by said timed means forintermittently disabling said responsive means over a predeterminedperiod following the return thereof to said day setting.

11. In a thermostat, temperature. responsive means movable betvi een dayand night settings, control means operable thereby, timed means formoving said responsive means from said night to said day setting, andmeans operable by said timed means for intermittently actuating saidcontrol means in a sequence of predetermined intervals extending over apredetermined period of time following the return of said responsivemeans to the day setting thereof.

12. In a thermostat, a base, a temperature responsive 'means pivotallysupported thereon and movable between day and night settings, switchmeans operable thereby, timed means supported on said base for movingsaid responsive means from said night to said day setting, and levermeans pivotally supported on said base and engageable with said switchmeans, said lever means being operable by said timed means forintermittently actuating said switch means in a sequence ofpredetermined intervals extending over a predetermined period of timefollowing the return of said responsive means to the day settingthereof.

13. In a thermostat, a base, a temperature responsive means pivotallysupported thereon and movable between day and night settings, switchmeans operable thereby, timed means supported on said base for movingsaid responsive means from said night to said day setting, cam meanssecured to said timed means for rotation therewith, a lever pivotallysupported on said base engageable with said switch means, means carriedby said lever engageable with said cam means and actuable thereby forintermittently actuating said switch means when said responsive means isreturned to the day setting thereof. Y

14. In a thermostat, a base, a temperature responsive means pivotallysupported thereon and movable between day and night settings, switchmeans operable thereby, manual means for moving said responsive meansfrom said day to said night setting, time means, said movement ofsaidmanual means setting said timed means in operation, means operableby said timed means to return said responsive means to said day settingafter a predetermined period or operation of said time means, cam meansoperable by said timed means, said cam means having a. series of spacedprojections, a lever pivotally supported on said,

base engageable with said switch means, and follower means carried bysaid lever engageable with said projections on said cam-means, said cammeans being radially retractable with respect to said timed means withmanual movement thereof, and said cam means being operable by action ofsaid timed means to intermittently actuate said switch means when saidresponsive means returns to the day setting thereof.

15. In condition control mechanism, anelement responsive to variationsin the value oi a condition, a control device operable thereby, saidelement being movable between first and second operating positionswherein it operates said control device so as to maintain first andsecond condition values, means for moving said element between said twopositions including a reversibly movable member, means for moving saidmember in opposite directions to cause said element to be moved betweensaid first and second operating positions, means including a cam elementcarried by said reversible movable member for causing intermittentoperation of said control device upon said element returning to saidfirst position by reason of the movement of said member in onedirection, and means for causing said cam element to be inefiective whensaid member is moving in the opposite direction.

16. In condition control mechanism, an ele-.

ment responsive to variations in the value of a condition, a controldevice operable thereby, said direction, and means for causing said camelement to move to an inoperative position when said member is moving inthe opposite direction.

17. In condition control mechanism, an element responsive to. variationsin the value of a condition, a control device operable thereby, saidelement being movable between first and second operating positionswherein it operates said control device so as to maintain first andsecond condition values, means for moving said element between said twopositions including a reversibly movable member, means for moving saidmember in a first direction to cause said element to be moved tosaid'second'operating position, timing means for moving said member inthe opposite direction to cause said element to be returned to saidfirst operating position at the end of a timed period, means including acam element carried by 50 said member for causing intermittent operationof said control device upon said element returning to said firstposition, and means for causins said cam element to be inefiectivemember is moving in said first direction. a

' CARL G. KRONWILER.

said element returning to said first position by reason of the movementof said member in one when said

